A direct injection type engine of directly injecting fuel into a cylinder is shorter in the time that elapses from when the fuel is injected until the fuel is combusted than an intake port injection type engine of injecting fuel into an intake port and hence cannot sufficiently earn the time required to vapor the fuel injected. Hence, the direct injection type engine needs to increase an injection pressure to a high pressure to thereby atomize the fuel injected. For this reason, in the direct injection type engine, the fuel suctioned from a fuel tank by a low pressure pump of an electrically driven type is supplied to a high pressure pump driven by the power of the engine and the high-pressure fuel discharged from the high pressure pump is pressure-fed to a fuel injection valve.
The high pressure pump of this type includes, for example, a pump described in JP-2010-533820A (US-2010-0237266A1) which is provided with a flow regulating valve for opening and closing an intake port side of the high pressure pump and with an electromagnetic actuator for moving the flow regulating valve to open and close the flow regulating valve and which controls the passage of current through the electromagnetic actuator to thereby control a period during which the flow regulating valve is closed, thereby controlling an amount of discharge of the fuel of the high pressure pump to control a fuel pressure (pressure of the fuel).
Further, as a technique for reducing noises caused when a fuel injection valve constructed of an electromagnetic valve is closed is proposed, for example, a technique disclosed in JP-4-153542A. In this technique, when the passage of current through a drive coil of a fuel injection valve (electromagnetic valve) is stopped to thereby close the fuel injection valve, the passage of current through the drive coil is stopped and then is again temporarily performed, whereby a valve closing speed of the fuel injection valve is decreased.
In the high pressure pump described above, when a valve-closing control of stopping the passage of current through the solenoid of the electromagnetic actuator to thereby move a movable part of the electromagnetic actuator to an opening-side position and to thereby open the flow regulating valve is performed, the movable part and the flow regulating valve are likely collide with a stopper or the like to cause vibrations and hence is likely to cause unpleasant noises by the vibrations.
As shown in FIG. 4, when the valve-opening control of a high pressure pump is performed, even if the passage of current through the solenoid is stopped, when fuel pressure in the pump chamber is yet high, even if the movable part hits the flow regulating valve, the flow regulating valve is held in a valve closing state by the fuel pressure in the pump chamber and hence the movable part is stopped in a state where the movable part abuts on the flow regulating valve. Then, when the fuel pressure in the pump chamber is decreased, the movable part is moved to the opening-side position and the flow regulating valve is opened.
For this reason, when the valve-opening control of the high pressure pump is performed, even if the passage of current through the solenoid is stopped at the same timing as a normal valve-closing control and then is again temporarily performed by the use of the technique disclosed in JP-4-153542A, as shown in FIG. 6, the passage of current through the solenoid is likely to be performed when the movable part hits the flow regulating valve and stops there. In this case, when the fuel pressure in the pump chamber is thereafter decreased to thereby move the movable part to the opening-side position, the moving speed cannot be decreased, which hence makes it difficult to reduce noises caused when the valve-opening control is performed.
When the valve-closing control of the flow regulating valve is performed, the movable part is likely to collide with a stopper part to thereby cause vibrations and hence unpleasant noises are likely to be caused by the vibrations. As a measure against this problem, in JP-2010-533820 (US-2010-0237266A1), is proposed the following technique: that is, a current value when current is passed through the flow regulating valve to thereby close the flow regulating valve is made a minimum current value, whereby a valve closing speed is decreased to thereby prevent the vibrations caused when the valve-closing control is performed.
However, the minimum current value capable of closing an electromagnetic valve is varied according to variations in manufacture and a usage environment (drive voltage and temperature), so that it is difficult to set a value of current passed through the electromagnetic valve at the minimum current value capable of closing the valve with high accuracy and hence a faulty valve closing operation incapable of closing the electromagnetic valve because of a shortage of current is likely to caused. Further, in order to secure a robust performance, a countermeasure such as a correction using the fuel pressure is required.
Hence, it is necessary to reduce noises caused when a valve-closing control is performed and to restrict a valve closing operation caused by a shortage of current.
Further, it is necessary to reduce noises caused when a valve-opening control of a high pressure pump is performed.